Central nervous system injury triggers a response cascade leading to activation of astrocytes, which participate in post-traumatic brain swelling. Studies have shown that the hormone 17beta-estradiol (E2) plays an important role in CNS injury, in part because of its beneficial effects on astrocytes. A voltage-dependent Ca2+ activated CI- (CICa) channel that is involved in mediating cell swelling was recently identified in freshly isolated native reactive astrocytes. It was also found that this channel can be activated by E2. This project aims to explore the nongenomic signaling cascade induced by E2 during its activation of this channel. Based on a cell line of immortalized astrocytes expressing the CICa channel, and using patch clamp electrophysiology and Western immunoblot as the basic methods of investigation, various activators and inhibitors of PLC, IP3 and PKC will be employed to pharmacologically characterize and plot the E2--CICa signaling pathway in a stepwise fashion. Elucidating E2's protective mechanisms in astrocytes activated by traumatic injury will contribute to the understanding of CNS response to injury, and holds the prospect of improving therapy for the unfortunate patients who suffer from such injuries.